There is a market for bioreactors and solid-state fermentation processes for the production of lignocellulosic enzymes and polysaccharides testing different fungal and bacterial strains so as to quantify the potential of each biosubstance.
Fungal polysaccharides can de exo-polysaccharides and endo-polysaccharides and are obtained by submerged fermentation and solid-state fermentation (SSF). The exo-polysaccharides, those excreted from the culture medium, have been obtained specially by means of submerged fermentation processes; whereas by using solid state fermentation intra-polysaccharides are specially obtained, which are found inside diverse fruit bodies of the macromycetes fungi and the mycelium.
The fruit bodies of the fungi are obtained by the method of culture in a bag or bed on formulated substrates with different natural organic materials subjected to culturing conditions required for each species so as to obtain competitive yields for the market.
These methods present scaling problems due to the difficulty of controlling variables such as heat transfer (difficult dissipation), mass transfer (heterogeneous interaction between all the molecules and in all directions within the substrate). These processes have shown to be more efficient in the production of enzymes up to a pilot scale.
By using SSF with filamentous fungi it has been possible to obtain better yields in the production of enzymes, lower problems of growth inhibition by substrates and greater stability of the organisms to changes in temperature and pH than when these organisms are cultured in liquid medium, and a lower occurrence of enzyme degradation by the presence of undesirable proteases.
There is a need for technological development around SSF, to explore how to obtain new substances using filamentous fungi, exploring the physiological characteristics presented during the development of the fungal cells in SSF processes, such as the accumulation of glycerol, eritritol and arabinitol which generate gene induction in glycoamylases, perhaps due to the activity of water under these process conditions.
The formation of secondary metabolites of numerous filamentous fungi during SSF is associated to the formation of the aerial hyphase and spores at the beginning of the secondary metabolism phase and is only described in these types of processes and not in submerged fermentation.
One of the strongest reasons stopping the advances in SSF processes are the design and engineering problems for standardization and scaling limiting the reproducibility of the results.
Management of temperature, humidity, and substrate concentration gradients increases during the process, generating adverse conditions in stationary solid bed processes and rolling drum reactors or other equipment with intermittent agitation. The correlation between environmental conditions, such as oxygen concentration, humidity levels and temperature make it hard to regulate these parameters.
Fungal development under aerobic conditions in the bioreactor results in a considerable increase in the production of heat caused by a rapid raise in temperature. This effect is desirable in composting processes, but is totally undesirable in in biotechnological processes in bioreactors since a large part of the enzymes produced during SSF can denaturalize at the end of the process.
Thus, the present invention improves the conditions for controlling temperature, humidity and oxygen concentration achieving optimal conditions for the production of bioactive substances by means of solid-state fermentation.